Lubricant composition and method of using same



April 15, 1969 B. E. COUNCIL ET AL 3,438,896

LUBRICANT COMPOSITION AND METHOD OF USING SAME Filed Sept. 9, 1965 TLEZINVENTORS' a BY VVAPQE-M M Woo/.75

United States Patent 3,433,896 LUBRICANT COMPOSTTION AND METHOD OF USINGSAME Bill E. Council and Warren W. Woods, Ponca City, Okla, assignors toContinental Oil Company, Ponca City, Okla, a corporation of DelawareFiled Sept. 9, 1965, Ser. No. 486,173 Int. Cl. ClGm 7/26, 3/22; Flori17/00 US. Cl. 25212 4 Claims ABSTRACT OF THE DISCLOSURE Lubricantcomposition comprising wax, wax-extendible copolymer and an extremepressure solid lubricant.

In one aspect the invention relates to a method of lubricating arailroad center plate assembly employing the above-described compositionin the form of solid pellets.

This invention relates to a lubricant composition for lubricating twometallic parts which move relatively to each other, and which includetwo opposed, relatively large bearing areas which are pressed againsteach other with a high compressive force. More particularly, but not byway of limitation, this invention relates to a method of lubricatingsuch parts, including especially, the method of lubricating the pivotalconnection between railroad cars and the trucks upon which the cars aremounted, and to the lubricant composition used in such method.

In the rail transport industry, certain standards have been adopted forrailroad car construction. In this standard construction, a centerbearing assembly is utilized to connect each of the railroad cars withthe trucks upon which the cars are mounted so as to permit the trucks tomove pivotally with respect to the cars, and thus to follow thecurvature of the tracks despite the inability of each of the cars toexactly follow or conform to such curvature. The center bearing assemblynow in substantially universal use includes a truck center plate havinga pivot pin extending vertically upward therefrom, and a body centerplate attached to the railroad car on the longitudinal centerlinethereof. The body center plate of the car acts as the load support forthe entire weight of the car, and this plate contacts the truck centerplate carried by the truck with the pivot pin functioning as theconnecting member and post about which the relative rotary motionbetween the car and the truck occurs.

The large contacting areas of the truck center plate and the body centerplate conjunctively wtih the heavy loading which is imposed upon thecenter bearing assembly results in a lubrication problem which has notheretofore been satisfactorily solved. The extent to which the car bodyis pivoted on the trucks in normal operation of the railroads is fromabout 3 to about dependent on the radius of curvature of the railroadtrack curve, and the pivotal movement of the car on the truck isrelatively slow. Thus, no opportunity is presented for conventional oilor grease type lubricants to enter between the body center plate and thetruck center plate and form a separating wedge of lubricanttherebetween. In other words, no occasion is afforded for the lubricantto penetrate between the two plates, and any lubricant which does enterinto this zone, or which has been initially placed there, is soonextruded from between the two plates and becomes ineffective forlubricating purposes.

A generally similar problem is frequently encountered in metal drawing,a process by which metal in its solid state is shaped by pressing itagainst a metal surface of nonc0nforming or differing configuration fromthe metal being shaped.

The present invention provides an improved method of ice lubricating theopposed surfaces of two metal members which move relatively to eachother, and which are pressed against each other under loads of largemagnitude. More specifically, the method of the invention has particularand special utility in the lubrication of center hearing assemblies ofthe type used on railway cars. The type of lubricating compositionutilized in practicing the method of the invention is believed to be anovel lubricant.

Broadly described, the method of the invention comprises positioningbetween two substantially monoplanar surfaces which are in bearingcontact with each other over a relatively large area, a lubricantcomposition which consists essentially of from about 20 to about weightpercent of a petroleum derived wax, from about 5 to about 50 weightpercent of a wax extendible copolymer, and from about 3 to about 40percent of an extreme pressure solid lubricant material, such asgraphite, molybdenum disulfide, or vermiculite. In a preferred method ofpracticing the invention, small solid particles of the lubricantcomposition are disposed between the contacting metal surfaces to belubricated at a time When the metal surfaces are spaced relatively farfrom each other, and prior to the positioning of these surfaces inbearing contact with each other. It is also preferred to positionbetween the metal bearing surfaces, an amount of the lubricantcomposition which exceeds the amount required to fill the void spacesbetween the surfaces and to form a film between the surfaces duringoperation of the bearing. The use of the excess lubricant permits aportion of the lubricant to be extruded from between the contactingbearing surfaces when the opposing metallic members are fully loaded,and the extruded portion of the lubricant solidifies adjacent the edgesof the plates which are in bearing contact, and this serves to form anencasing shield around the joint which prevents infiltration of dirt,water and other deleterious materials between the bearing surfaces.

Important broad objects of the invention are to provide a new lubricantcomposition and an improved method of lubrication.

Another, more specific object of the invention is to provide a lubricantcomposition which functions superiorly to other lubricants inlubricating opposed metal surfaces in instances where the surfaces areeach of relatively large surface area, and are pressed against eachother :by

' forces of large magnitude.

A further object of the invention is to provide a method of lubricationby which an effective lubricant may be interp'osed between two bearingsurfaces, and a sealing film or shield substantially simultaneouslyformed around the junction line of the bearing surfaces so as to excludedust, water and other deleterious materials from between the bearingsurfaces.

A more specific object of the invention is to provide an improved methodof lubricating the center plate assembly used to support railroad carson their respective trucks.

Another object of the invention is to improve the ease with which metaldrawing can be accomplished, such improvement being effected through theuse of the new lubricant of this invention.

Additional objects and advantages will become apparent as the followingdetailed description of the invention is read in conjunction with theaccompanying drawing which illustrates certain aspects of the invention.

In the drawing:

FIGURE 1 is a plan view of a railroad car and illustrating in dashedlines, the position of the trucks and the center plate assembliesbeneath the car.

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1.

Before referring specifically to the drawings which depict a centerplate assembly to which the method of the invention can be especiallybeneficially applied, the lubricant composition utilized in the methodof the invention will be discussed. The composition is basically athreecomponent system and consists essentially of a petroleumderivedwax, a wax compatible copolymer and an extreme pressure solid lubricant.The petroleum-derived wax utilized may be, for example, a paratfin waxor a microcrystalline wax prepared by any of the methods now in use andwell understood in the petroleum refining industry. Excellent resultshave been obtained utilizing a crude scale paraffin wax having a meltingpoint of from about 125 F. to 135 F. and a maximum oil content of about1.5 percent. Parafiin waxes of widely varying melting points and oilcontents can be utilized successfully, however, and microcrystallinewaxes are also suitable, though generally less desirable, for use in thelubricant composition. The amount of the wax employed can vary widely,and will depend upon the chemical character and the quantity of theother materials used in the composition. In general, however, from about20 weight percent to about 80 weight percent of the wax should beutilized in the composition. An amount of from about 40 to about 70weight percent is preferred.

The second major ingredient of the composition is a copolymeric materialwhich is compatible with the wax, and which is a so-called waxextendible material. Examples of copolymers of this type areethylene-vinyl acetate, ethylene-ethyl acrylate, and ethylene-isobutylacrylate. The preferred copolymer for use in the lubricant compositionis an ethylene-vinyl acetate copolymer, such as that sold under thetradename Elvax by the E. I. du Pont de Nemours Company, of Wilmington,Del. The copolymer functions in the composition as a plasticizing agentto give the proper retention properties to the solid extreme pressurelubricant material hereinafter described, and to form a cohesive mixtureof the wax with the solid lubricant. The quantity of the wax extendiblecopolymer utilized can vary widely, but in general, should be at least asufficient amount to prevent the composition from having an oilytexture. From about 5 weight percent to about 50 weight percent of thecopolymer can generally be employed in the composition, with weightpercent to about weight percent usually being preferred.

The third major ingredient of the lubricant composition is an extremepressure solid lubricant material. Materials of this type are well knownin the art and include, for example, graphite, molybdenum disulfide andvermiculite. The amount of solid lubricant used may range from 3 toweight percent and is preferably from about 10 to about 30 weightpercent. In general, it is preferable to use about 5 to about 10 weightpercent less vermiculite in lubricants containing this material than theamount of graphite or molybdenum disulfide which would be optimum in thesame composition.

In preparing the lubricant composition, the wax and copolymer are heatedso as to convert these materials to a molten state and the liquids arethen blended together in any suitable mixing device. The solid extremepressure lubricant is reduced to a finely divided or powdered state andis thoroughly dispersed in the molten wax-copolymer blend so as toachieve an evenly distributed dispersed phase in the blend. Thecomposition is then permitted to solidify and is pelletized into smallsolid pellets. The lubricant is applied in most lubricating applicationsin the pellet form, as will be hereinafter described in greater detail,but it should also be noted that, in some instances, such as in metaldrawing, it will be preferable to lubricate bearing surfaces by heatingthe lubricant composition to a molten state and painting or covering thecontacting surfaces with the molten composition and then permitting itto solidify in situ. It should also be pointed out that in a metaldrawing operation involving stamping, the lubricant has been effectivelyused by casting a thin film of the lubricant (10 to 20 mils inthickness) and placing the film between the plate to be stamped and thefemale die of the stamping machine.

As has been previously indicated herein, an important specific aspect ofthe present invention is the utilization of the method of the inventionin lubricating the center plate assemblies used to connect railroad carsto their respective supporting trucks. A typical center plate assemblyis depicted by the accompanying drawings. A railroad car 10 is supportedon a forward truck assembly 12 and a rear truck assembly 14. Asillustrated in FIG- URE 2, the car body It} carries a body center plate16 at each end thereof. The respective body center plates 16 rest upon acar truck center plate 18 which is mounted on a truck bolster 20. Thetruck bolster 20 extends between and is connected to a pair of parallelwheel supporting frame members 22. Each body center plate 16 isconnected to its respective truck center plate 18 by a pivot pin 24which is either connected to the truck center plate and extends upwardlythrough an aperture in the body center plate, or is extended throughaligned apertures in both of the plates to pivotally interconnect thetwo plates. When the car body 10 is connected to the truck assemblies 12and 14, the entire weight of the car and its cargo is transmitted to thetruck wheels 26- through the body center plate 16 and the truck centerplate 1 8 which are in bearing contact with each other. As the trainnegotiates a curve, the car body 10 and its associated body centerplates 16 pivot with respect to the truck assemblies 12 and 14. Ingeneral, each of the body center plates 16 will rotate through an angleof up to about 10 about the pivot pin 24.

In using the method of the present invention to lubricate a center plateassembly, a number of the lubricant pellets formed as hereinbeforedescribed are placed upon the upwardly facing truck center plate 18while the car 10 is removed from the trucks. In general, about one poundof the lubricant pellets will be adequate for the lubrication of each ofthe standard center plate assemblies. After the pellets have been evenlydistributed on the upwardly facing surface of the truck center plate 18,the car 10 islowered into position so that the body center plate 16carried by the car is centered on the truck center plate and isconnected thereto by the upwardly extending pivot pin.

As the weight of the car 10 is brought to bear on the center plateassembly, the pressure generated in the assembly by the weight of thecar body is sufficient to cause the lubricant to have plastic flowproperties and t0 fill all of the voids between the opposed or facingsurfaces of the truck center plate 18 and the body center plate 16. Theslight excess of lubricant which is preferably provided is extrudedaround the edges of the center plates and resolidifies after extrusionto form a surrounding shield which protects the space between the platesagainst the entry thereinto of dirt, Water and other deleteriousmaterials.

The lubricant composition of the invention has been markedly moreeffective in lubricating center plate assemblies of the type describedthan conventional lubricants which have heretofore been employed in thisenvironment. The effectiveness of the lubricant is due to the collectiverole played by each of the major constituents of the composition in theoverall lubricating function. It appears that the wax lubricates theassembly in substantially the same manner as grease or oil interposedbetween the bearing surfaces. The solid extreme pressure lubricant, suchas graphite or molybdenum disulfide, lubricates the high pressuremetal-to-metal points which exist between the metal faces due tonon-conformites and asperities. Although the copolymer may have somelubricating properties, its primary role is as a plasticizing agentfunctioning to give the proper retention properties of the lubricant inthe bearing.

An example of the use of the lubricant of the invention in lubricatingthe center plate assembly of railroad cars will serve to further clarifythe manner in which the invention is to be practiced. 56 weight percentof a parraffin Wax of crude scale wax grade and having a melting pointof 128 F. and a maximum oil content of 1.5 Weight percent was blended inthe molten state with 14 weight percent of an ethylene-vinyl acetatecopolymer having the following properties:

Wt. percent ratio, ethylene: vinyl acetate 72:28 Melt index (A'STM Dl238-57T 22 to 28 Refractive index, N 1.485 Density at 30 'C., grams/cc.0.95 Softening point (ring and ball), F 307 Inherent viscosity, cp. 30C. 0.78

After thoroughly mixing the wax and ethylene-vinyl acetate, 30 weightpercent of finely divided lubrication grade graphite was thoroughlydispersed in the molten waxcopolymer blend. The composition was thenpermitted to solidify and was pelletized int-o pellets having a diameterof about lit; inch and an indiscriminate length which was usuallybetween about A inch and /3 inch.

About one pound of the pelletized lubricant was placed on the truckcenter plate of a railroad car center plate assembly and the car thenlowered into position on the truck. A small amount of the lubricant wasextruded between the opposed surfaces of the body center plate carriedby the car and the truck center plate carried by the truck. Thisextruded portion of the lubricant solidified outside the bearing andformed a protective shield preventing entry of dirt and water into thebearing. The lubricant thoroughly lubricated the center plate assemblyover an extended period of time and, in general, performed moresatisfactorily than conventional lubricants of the type previously usedin the lubrication of center plate assemblies.

The same lubricating composition used in the example of the lubricationof a railroad center plate assembly as described above was used in ametal drawing operation where a fatty type conventional lubricant hadpreviously been used without success. The operation involved stamping 4inch pipe caps from inch steel plate using a 93- ton Bliss side-crankpress. When the conventional lubricant was used the caps wereunsymmetrical and were excessively scufied and scarred. When thelubricant of the present invention was used, symmetrical stampings wereobtained which displayed very little scufiing.

From the foregoing description of the invention, it will have becomeapparent that the invention provides an improved method of lubricationutilizing a novel lubricant composition. The eifectiveness of thelubricant for lubricating the center plate assemblies of railroad carsis particularly marked.

Although certain specific embodiments of the invention have been hereindescribed in order to provide examples of its practice as guidelinessuflicient for those having skill in the art to which the inventionappertains, it will be apparent that other materials in addition tothose specifically mentioned can be included in, and made a part of, thelubricating composition, and that other steps may be included in thelubricating method without departure from the basic principles hereinenunciated and which constitute the foundation of the invention.Therefore, modifications and innovations in the practice of theinvention which continue to rely on the basic principles underlying theinvention are deemed to be circumscribed by the spirit and scope of theinvention except as the same may be necessarily limited by the appendedclaims or reasonable equivalents thereof.

What is claimed is:

1. A solid lubricant composition in the form of solid pellets andconsisting essentially of from about 20 to about weight percent of apetroleum derived wax, from about 5 to about 50 weight percent of awax-extendible copolymer selected from the group consisting ofethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymersand ethylene-isobutyl acrylate copolymers, and from about 3 to about 40weight percent of an extreme pressure solid lubricant, selected from thegroup consisting of graphite molybdenum disulfide and vermiculite.

2. A solid lubricant composition as claimed in claim 1 wherein saidcomposition consists essentially of from about 40 to about 70 weightpercent petroleum derived wax, from about 10 to about 25 weight percentof Wax extendible copolymer, and from about 10 to about 30 weightpercent of extreme pressure solid lubricant.

3. A lubricant composition as claimed in claim 1 wherein said wax isparaffin wax, said wax extendible copolymer is ethylene-vinyl acetateand said solid lubricant is graphite.

4. A solid lubricant composition consisting of about 56 weight percentof a paraffin wax having a melting point of from about F. to about F.and an oil content not exceeding 1.5 weight percent; about 1'4 weightpercent of an ethylene-vinyl acetate copolymer having a vinyl acetatecontent of about 2'8 Weight percent and a melt index of from 22 to 28;and about 30 weight percent of graphite.

References Cited UNITED STATES PATENTS 3,097,'169 7/ 1963 Hall '102383,213,024 10/1965 Blake et a1 252-18 3358,6 19 6/ 1966 'Cox 2'5Q593,264,215 8/1966 Smith et a1 252- 12 DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

US. Cl. X.R.

